1. Field of the Invention
The invention relates to compacting machines and, more particularly, relates to an improved water supply system for a vibratory plate machine of the type used to smooth and compact hot or cold mix asphalt.
2. Discussion of the Related Art
Vibratory plate machines, usually known simply as "vibratory plates" are widely used in the construction and landscaping industries for the compaction of granular materials. Applications include the compaction of sand, gravel, or crushed aggregate for foundations, footings, or driveways; base preparation for concrete slabs, asphalt parking lots, etc.; and the compaction of either hot or cold mix asphalt during patch or repair of streets, highways, sidewalks, parking lots, etc. The typical vibratory plate machine includes a baseplate that performs the actual compacting operation and a console that is mounted on the baseplate so as to support an engine and its associated equipment. An eccentric shaft device, commonly known as an exciter, is located on the baseplate in an underlying relationship to the console and is driven by the engine to impart vibrations to the baseplate, thereby compacting materials on which the machine rests. Movement of the machine is controlled by a handle assembly extending upwardly and rearwardly from the console.
In hot or cold mix asphalt compaction applications, the machine is additionally provided with a water supply system for spraying water or another lubricant onto the asphalt surface immediately in front of the machine to prevent the asphalt from congealing on the baseplate. The typical water supply system includes 1) a storage tank mounted directly or indirectly on the console and 2) a nozzle assembly or spray bar mounted on the front end of the baseplate. A tube connects a bottom opening in the storage tank to a central opening of the spray bar such that water flows by gravity from the storage tank to the spray bar. Water is discharged from the spray bar and onto the asphalt surface via a plurality of spray orifices directed toward the asphalt surface. Spraying of water onto the asphalt surface directly in front of the asphalt finishing machine serves to lubricate the surface and to prevent or at least inhibit sticking or congealing of asphalt on the baseplate.
Water supply systems of the described type suffer from noticeable drawbacks and disadvantages due to the fact that they are gravity fed rather than pressurized.
For instance, it is desirable to maintain a generally constant, designated flow rate of water out of the spray orifices so that the proper amount of water is sprayed onto the asphalt surface for lubrication. Spraying too much water might degrade the quality of the compacted surface. Spraying too little water might hinder the lubrication effectiveness of the system. Spraying water at a generally constant rate is impossible with gravity fed systems of the above-described type because the flow rate of water from the spray bar is primarily a function of the static pressure head within the storage tank which, of course, falls steadily as the storage tank empties. Accordingly, sizing the tubes and orifices properly to assure an ideal water flow rate from a full storage tank might lead to inadequate lubrication when the storage tank is nearly empty.
Moreover, the absence of pressure hinders the ability of the system to spray a uniform pattern when the machine is operating on a side slope because the unpressurized water tends to run to and be discharged from the downstream end of the spray bar. This uneven flow leads to a reduction or even absence of lubricant flow from the orifices near the upstream end of the spray bar.
The need therefore exists to provide a water supply system for an asphalt vibratory plate machine that assuredly sprays water or another lubricant onto the asphalt surface at a generally uniform rate regardless of machine inclination.